178 REPRESENTATION OF THE 



ence of a distinct topical life. The hairs and teetli of ani- 

 mals generally, and the antlers of the deer, have already 

 been cited as furnishing illustrations of it. The first set of 

 teeth, for instance, are formed each in its own capsule by a 

 process of local growth, quite independent of that of the 

 neighbouring tissues, nay, in so far opposed to it, that at a 

 certain stage of development the integuments of the gum 

 are partially disintegrated to allow of their eruption. A 

 tooth, thus generated by independent growth, some time 

 after attaining maturity, undergoes a process of decay, end- 

 ing in its ultimate removal, when a new tooth of the second 

 dentition takes its place by a similar process of local growth. 

 In its turn this tooth also is shed, and though in most 

 species it has no successor, yet in a few there is a constant 

 succession during the whole lifetime of the animal ; and 

 this is the general rule in the case of the hair.* Hence in 

 such local formations as teeth, hair, &c., we have, in the 

 way they are marked off from the neighbouring parts, and 

 in this succession of growth, maturation, and decay re- 

 peated again and again, and epitomizing, as it were, the life 

 of the animal on which they grow evidence of a vitality, 

 quite as defined perhaps in itself as that presented by the 

 free zooids of the lower species, though their functional 

 dependence on the common circulation, and the mechanical 

 bond of a common integument, prevent their exhibiting the 

 more obvious phenomena of a separate life. But as we 

 descend in the scale of organization we come to species, 

 where, from the absence of centralizing influences, the se- 

 veral organs which are possessed of a vitality, less ener- 

 getic perhaps, but more enduring than in the higher be- 

 come emancipated, as it were, from the control of the 

 general system, and appear as zooids, that is, in the guise 



* Paget's Lectures on Surgical Pathology. Kirkes* Handbook of 

 Physiology, Ch. X. 



